Very often buildings which are being constructed, particularly high-rise buildings, such as apartments and office buildings, have poured concrete floors. The thickness of the concrete which is poured to form a floor may be up to eight inches, depending on the span of the floor between supporting walls or structures, and sometimes higher. In any event, in most instances, concrete floors are poured in spans of up to eighteen feet, which spans are between supporting walls or pillars. However, during the construction of a high-rise building, it is necessary to provide forming structures to support each of the concrete floors as it is poured and for the next few days following when it is poured, so as to permit the concrete to cure sufficiently in order to remove the forming from beneath it.
Thus, most often, a concrete floor in a high-rise building is prepared by pouring the concrete on a form which is supported on the floor beneath the one being poured, and which provides a substantially flat or planar upper deck on which the concrete is poured. When the concrete forming is subsequently removed after the flooring has cured, each span of the floor is supported by columns or shear walls, having spans up to eighteen feet and sometimes greater, and having a depth which is the front to back dimension of the building being constructed. Very often, therefore, concrete floors are poured in bays between columns or supporting walls which may have dimensions of up to eighteen feet (or twenty feet) by up to eighty feet.
It is desirable to move the concrete forming structure on which the concrete floor is poured as easily as possible; and this is most easily accomplished by moving the concrete forming structure substantially as one integral structure. Otherwise, it is necessary to provide a plurality of forms including steel or wooden crib-like structures or scaffolding, individual plywood sheeting to form the deck on which the concrete is poured, etc. When the concrete forming structure can be moved in substantially one operation as one integral structure, labour costs can be considerably reduced--both in respect of set-up time and knock-down time--as well as in the use of labourers rather than semiskilled or skilled tradesmen and journeymen. Thus, flying forming systems have been developed whereby a concrete forming structure is built as a single, monolithic or integral structure having trusses, beams and a deck set up as a single entity. The flying form is so called because it can be "flown" from one bay to another using tower or self-climbing cranes of the type well known in the construction industry. A high-rise building may therefore be constructed using a plurality of flying forming structures as concrete forming structures in the following manner:
When the first floor at or slightly above ground level has been poured on suitable concrete forming structures, a plurality of flying forms are placed on it, one or more for each bay as discussed hereafter, depending on the type of flying form and depending on the materials to be used. In any event, the second floor to be poured--i.e. the first floor to be poured using the flying forms--together with the appropriate walls or columns, are then poured using the flying forms as well as appropriate wall or column forms, as required. In the usual case, a second set of flying forms is then placed on the concrete floor after sufficient time has passed that the curing concrete will at least support the weight of the concrete forming structure or flying form to be placed on it, as well as the weight and impact of boots, etc. of the workers. Suitable column or wall forms are also placed, and the second poured concrete floor is formed. At this time, the first poured concrete floor may be sufficiently cured to permit removal from beneath it of the first set of concrete forming structures--the flying forms--on which that floor has been poured. Otherwise, a third set of flying forms is placed on the second poured floor using suitable tower or self-climbing cranes--together with the appropriate column or wall forms--and a third concrete floor is thereby poured. Usually, by this time, the first floor which was poured has sufficiently cured to permit removal of the first set of flying forms, if they have not already been removed for construction of the third floor.
In order to remove the flying forms, they are first lowered from the underside of the concrete floor which was poured on them, and then they are pushed outwardly from the building and secured to suitable cables extending downwardly from the outwardly extending arm of a crane. Each form is then flown by lifting it upwardly with the crane and placing it on the last-to-be-poured concrete floor, together with appropriate column or wall forms, for use as a concrete forming structure on which yet another concrete floor is to be poured. Therefore, in the usual case, a flying form is used as a concrete forming structure in a bay which may be many storeys high, by "leap-frogging" the flying form past one or two other flying forms and placing it on the then uppermost poured concrete floor in order that yet another floor can be poured on it, and so on. Thus, as few as two--and usually three--flying forms per bay may be required for the construction of a multi-storeyed high-rise building.
It has been found, however, when flying forms are heavy, and tower or self-climbing cranes are restricted as to the weight that they can handle--particularly when the lifting point is considerably far out on the horizontal lifting arm of the crane, that this can be overcome by the use of flying forms as concrete forming structures when the flying forms comprise truss and beam members which are formed of aluminum. In any event, however, this invention provides a flying form as a concrete forming structure wherein the deck on which the concrete is poured is easily and readily secured to the upper edges of a plurality of beams which are set transversely across a pair of truss members. This latter advantage is gained by providing a beam structure having an upper section in the form of an inverted top hat which is open at its upper end and which is adapted to graspingly secure wooden joist members which may be driven downwardly into the top hat open section and to which the panels comprising the upper deck may be fastened using drivable fastening means, such as nails or screws.